nslookup - query Internet name servers interactively
nslookup [-option] [name | -] [server]
nslookup is a program to query Internet domain name
servers. nslookup has two modes: interactive and non-interactive.
Interactive mode allows the user to query name servers for information about
various hosts and domains or to print a list of hosts in a domain.
Non-interactive mode prints just the name and requested information for a
host or domain.
Interactive mode is entered in the following cases:
- a.
- when no arguments are given (the default name server is used);
- b.
- when the first argument is a hyphen (-) and the second argument is the
host name or Internet address of a name server.
Non-interactive mode is used when the name or Internet address of
the host to be looked up is given as the first argument. The optional second
argument specifies the host name or address of a name server.
Options can also be specified on the command line if they precede
the arguments and are prefixed with a hyphen. For example, to change the
default query type to host information, with an initial timeout of 10
seconds, type:
nslookup -query=hinfo -timeout=10
The -version option causes nslookup to print the
version number and immediately exit.
- host
[server]
- This command looks up information for host using the current
default server or using server, if specified. If host is an
Internet address and the query type is A or PTR, the name of the host is
returned. If host is a name and does not have a trailing period
(.), the search list is used to qualify the name.
To look up a host not in the current domain, append a period
to the name.
- server domain |
lserver domain
- These commands change the default server to domain; lserver
uses the initial server to look up information about domain, while
server uses the current default server. If an authoritative answer
cannot be found, the names of servers that might have the answer are
returned.
- root
- This command is not implemented.
- finger
- This command is not implemented.
- ls
- This command is not implemented.
- view
- This command is not implemented.
- help
- This command is not implemented.
- ?
- This command is not implemented.
- exit
- This command exits the program.
- set
keyword[=value]
- This command is used to change state information that affects the lookups.
Valid keywords are:
- all
- This keyword prints the current values of the frequently used options to
set. Information about the current default server and host is also
printed.
- class=value
- This keyword changes the query class to one of:
- IN
- the Internet class
- CH
- the Chaos class
- HS
- the Hesiod class
- ANY
- wildcard
The class specifies the protocol group of the information. The
default is IN; the abbreviation for this keyword is cl.
- nodebug
- This keyword turns on or off the display of the full response packet, and
any intermediate response packets, when searching. The default for this
keyword is nodebug; the abbreviation for this keyword is
[no]deb.
- nod2
- This keyword turns debugging mode on or off. This displays more about what
nslookup is doing. The default is nod2.
- domain=name
- This keyword sets the search list to name.
- nosearch
- If the lookup request contains at least one period, but does not end with
a trailing period, this keyword appends the domain names in the domain
search list to the request until an answer is received. The default is
search.
- port=value
- This keyword changes the default TCP/UDP name server port to value
from its default, port 53. The abbreviation for this keyword is
po.
- querytype=value
| type=value
- This keyword changes the type of the information query to value.
The defaults are A and then AAAA; the abbreviations for these keywords are
q and ty.
Please note that it is only possible to specify one query
type. Only the default behavior looks up both when an alternative is not
specified.
- norecurse
- This keyword tells the name server to query other servers if it does not
have the information. The default is recurse; the abbreviation for
this keyword is [no]rec.
- ndots=number
- This keyword sets the number of dots (label separators) in a domain that
disables searching. Absolute names always stop searching.
- retry=number
- This keyword sets the number of retries to number.
- timeout=number
- This keyword changes the initial timeout interval to wait for a reply to
number, in seconds.
- novc
- This keyword indicates that a virtual circuit should always be used when
sending requests to the server. novc is the default.
- nofail
- This keyword tries the next nameserver if a nameserver responds with
SERVFAIL or a referral (nofail), or terminates the query (fail) on such a
response. The default is nofail.
nslookup returns with an exit status of 1 if any query
failed, and 0 otherwise.
If nslookup has been built with IDN (internationalized
domain name) support, it can accept and display non-ASCII domain names.
nslookup appropriately converts character encoding of a domain name
before sending a request to a DNS server or displaying a reply from the
server. To turn off IDN support, define the IDN_DISABLE environment
variable. IDN support is disabled if the variable is set when
nslookup runs, or when the standard output is not a tty.
Internet Systems Consortium
2023, Internet Systems Consortium